In Vitro Fertilization (IVF)
Interpreting IVF Success Rates
IVF centers are required to report their IVF success rates annually to Centers for Disease Control and Prevention (CDC) and Society for Assisted Reproductive Technologies (SART). Although CDC and SART explicitly warn patients against using reported success rates to choose an IVF center for various reasons, for many patients, understandably, these published IVF success rates are an important factor in making this decision. Here, we provide a guide to help patients interpret the published IVF pregnancy rates to make an educated decision.
The important thing to remember is that the center with the highest pregnancy rates may not be the best center for every patient, however counter-intuitive it may sound. Caution is particularly important given the recent discovery (by CHR physicians, reported in a 2013 Fertility & Sterility article) that a handful of large IVF centers are manipulating their IVF outcome reporting so that their pregnancy rates will appear higher to gain market advantage.
What are IVF success rates & how are they calculated?
IVF success rates are essentially the pregnancy rates after IVF. There are several ways to calculate IVF success rates, but all IVF success rates are calculated by dividing the number of favorable results (number of live births, for example) by the number of procedures performed (number of embryo transfers, for example). Even in a single IVF center, IVF success rates can vary depending on how the end point is determined, and which procedure is used as a base.
The two major types of IVF success rates are the clinical pregnancy rate and the live birth rate.
Clinical pregnancy rate is used most often when the number of live births is not yet available. Because a pregnancy takes about 40 weeks to reach full term, IVF centers that want to publish their pregnancy rates before all their patients reach that end point must use clinical pregnancy rate when reporting their outcomes. This is the IVF success rate that we publish at CHR, because we believe that our patients should know our IVF pregnancy rates as soon as they are available, rather than waiting for a year or more.
However, patients are probably most interested in the live birth rate, the likelihood of having a "take-home baby" after an IVF cycle. Live birth rate tracks each pregnancy, established through IVF, all the way to delivery (though some will inevitably end in miscarriages). This is the IVF pregnancy rate that the CDC/SART publishes every year. Unfortunately, it takes more than a year for the CDC/SART pregnancy rates to become available, raising the concern that the published data may be too old to be representative of an IVF center's current performance.
How to Use IVF Success Rates to Find the “Right” IVF Center
When looking for an IVF center to work with, many educated infertility patients look at each IVF center's published IVF success rates. IVF pregnancy rates do have their place in the fertility center selection process. However, it is practically impossible to compare fertility centers by comparing their clinical outcomes primarily because of patient selection bias, and more recently due to manipulations of outcome reporting by some major IVF centers.
The problem of selection bias exists in other medical specialties. For example, Medicare annually publishes mortality rates for coronary bypass surgeries. Guess who has the highest mortality rates? It's the best surgical units, because these are the units that accept and treat the most difficult cases, which, unsurprisingly, results in these excellent centers having the highest mortality rates. Due to the bias in patient selection, paradoxically, the best surgical units end up with the worst "success rates."
The same principle applies to infertility programs, and especially to IVF. The days where IVF laboratories had their "little secrets" are long gone. Today, IVF has in many ways become a commodity in that almost every halfway decent IVF program will have good pregnancy outcomes in average patients, as long as they control age of their patients and make sure that they only select patients with reasonable ovarian reserve.
U.S. IVF programs have been excellent in selecting such favorable patients, and over 30 years, year after year, have improved national pregnancy rates, as reported to CDC and SART. The figure below shows the rising trend of IVF success rates, nationwide, with the exception of women over 42, where the rate has fallen slightly.
At the same time, patients who are more "difficult" to manage are getting the shaft: If their FSH is a little high or their AMH low, they are turned away from IVF; If they do not produce at least 4-5 follicles, their cycles are cancelled; If, God forbid, they are above age 42-43, forget it! Some fertility centers, unfortunately, exclude these patients—at least partially—in order to maintain their high IVF success rates.
In Europe, where pregnancy rates after IVF are much lower than in the U.S, things are even more discriminatory. Since governments in many countries control health care, including coverage for IVF, they also determine coverage limits. In some Scandinavian countries, you are simply not eligible for IVF after 40, 41 or 42 (depending on the country).
We bring this up here, because the patient population defines results. Just as more severe cases of coronary heart disease, even in the best surgical hands, will have higher mortality rates than milder cases, IVF outcomes vary in favorable and less favorable patient populations.
CDC and SART probably have made this point best when noting that their annual reports should not be used "to compare IVF programs." Inferior IVF programs can easily produce pretty good pregnancy rates if they carefully select their patients. Even superior programs with advanced techniques, in contrast, may have lower success rates, if those programs treat patients who have a long history of fertility treatment and highly complex case of infertility.
Publication of CHR's 2013 finding that a small number of IVF centers may be manipulating their IVF outcome reporting to skew higher by abusing some of the loopholes in the reporting rules only emphasize the point. The study, published in the journal Fertility & Sterility, identified 13 IVF centers that excluded a disproportionately large number of older women (who are expected to have poorer pregnancy chances) from their outcome reporting, thereby artificially inflating their reporting IVF success rates. These centers reported significantly higher pregnancy rates than all other IVF centers during the study period of 2005-2010. Clearly, however, whether these higher pregnancy rates would apply to older women seeking IVF at these centers is less than certain.
Therefore, to select a fertility center or IVF program based on reported IVF pregnancy rates can be extremely misleading. More importantly, basing the IVF program choice solely on high IVF success rates may delay actual treatment for some patients—especially if they fall into the "difficult cases" category. IVF centers with high IVF success rates may exclude these patients from treatment (if not from reporting), cancel their IVF cycles, or delay the IVF cycle start "until FSH levels, hopefully, improves" (which should not be expected to happen, since FSH usually only goes up).
How to Interpret IVF Success Rates
When you are trying to select an IVF center for your treatment, there are a few things to keep in mind.
- Unless you already know - from previous physician consultations and/or comprehensive testing - that your case is simple, beware of IVF centers with exceptionally high IVF success rates. Chances are, they have strict patient exclusion criteria that might exclude you.
- It is always a good idea to ask, before you make your first appointment, whether the fertility center has any predetermined cut-off values. Cut-off values might be the FSH level, number of follicles on ultrasound, or simply age.
- Look at the center's IVF success rates in their egg donor programs. Pregnancy rates in egg donor program are typically not influenced by patient selection. If a fertility center has a good IVF pregnancy rates in its egg donor program, the center is more likely to be skilled at IVF techniques. (See below for details.)
The correct question to ask in selecting a fertility treatment center is not simply "What are the center's pregnancy rates?" but "Who are the patients the center treats, and what are their pregnancy rates?" IVF success rates do matter, but only within an appropriate context that takes into account who is treated, who is refused treatment, and whose (likely negative) outcomes are not reported. This approach also reassures that you will fit the IVF program's criteria as a patient.
Egg Donation Programs as Quality Measure
While we at CHR fully support CDC and SART in rejecting IVF pregnancy rate outcomes as criteria to compare IVF centers, there is one IVF outcome data that is much less subject to patient selection manipulation: the pregnancy rate in egg donor cycles.
Egg donor cycles are much less affected by IVF centers' patient selection, because most egg donors are comparable to each other, unlike infertility patients. All IVF centers with an egg donor program recruit donors who are young and have normal ovarian reserve. If all centers are treating a mostly uniform population (egg donors in this case), their outcomes should be a relatively good measure of their skills in IVF.
We advise our patients to look at egg donor cycle outcomes as a relatively less biased outcome parameter. IVF success rates in egg donor cycles, at least to some degree, allows comparisons between IVF centers. A program with excellent egg donor pregnancy rates must be doing something right. Good IVF pregnancy rates cannot be achieved unless the center's clinical and laboratory divisions function well, and this is reflected in each center's success in egg donor cycles.
If a fertility center with respectable donor pregnancy rates has lower pregnancy rates in their general (non-egg donor) IVF program, it probably means that the program is more welcoming toward patients with more difficult cases, like older women, younger women with severely diminished ovarian reserve, women with autoimmune issues and other medical conditions affecting their fertility.
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Last Updated: April 10, 2017